The present invention relates to a new compound, 2-ethoxymethyl-5-hydroxy-.gamma.-pyrone, and a melanogenesis-inhibiting endermic preparation for external application which contains the same new compound as an active ingredient and which is effective for curing and preventing pigmentation diseases such as chloasma, senile moles, sunlight-induced moles or pigmented spots after inflammation and for whitening human skin.
In order to remove freckles, spots or the like as appear on the skin, a cosmetic material containing a peroxide such as hydrogen peroxide or zinc peroxide has been used for a long time.
However, since the peroxides are extremely unstable, they have some difficulties when stored and when incorporated into cosmetic bases. Additionally, they do not have a sufficient skin-whitening effect.
Further, cosmetic materials containing vitamin C, cysteine, colloidal sulfur or the like have been used for the purpose of skin-whitening, but the effect of the additives is not sufficiently satisfactory.
Recently, kojic acid has been found to be a substance having an excellent effect for inhibiting formation of melanin in human skin. Accordingly, there have been developed a kojic acid-containing whitening cosmetic material (JP-B-56-13569--the term "JP-B" as used herein means an "examined Japanese Patent Publication), a skin-whitening cosmetic material containing an ester of kojic acid with an aromatic carboxylic acid such as cinnamic acid or benzoic acid (JP-B-60-10005), and a skin-whitening cosmetic material containing a monoester of kojic acid with an aliphatic carboxylic acid (JP-B-61-60801 and 60-7961).
As mentioned above, kojic acid and kojic acid esters are excellent substances for inhibiting formation of melanin. It is known that, when the substances are incorporated into cosmetic materials or endermic preparations for external application as a main component thereof and are applied to the skin, they display an excellent skin-whitening and melanogensis-inhibiting effect without injuring the skin. However, other substances having a higher melanogensis-inhibiting effect are greatly desired in this technical field.